1. Field of the Invention
The present invention relates to an electronic device and a method of manufacturing the same. More particularly, the present invention relates to an electronic device in which a functional element and a switching element are bonded vertically, and a method of manufacturing the same.
2. Description of the Related Art
Among electronic devices, memory devices are used in almost all electronic equipment. Demand for nonvolatile memory devices continues to increase.
Nonvolatile memory devices include a ferroelectric random access memory (FRAM). An FRAM includes one metal oxide semiconductor (MOS) transistor and one ferroelectric capacitor. The ferroelectric capacitor includes a lower electrode, a ferroelectric layer and an upper electrode, which are stacked in sequence. The ferroelectric layer is stacked on the lower electrode in an amorphous state. Thus, after the ferroelectric layer is formed, an annealing process is performed to crystallize the ferroelectric layer. Although the annealing process is performed differently depending on the kind of the ferroelectric layer used, the annealing process is generally performed in an oxygen atmosphere at a temperature of 600° C. or more.
In a conventional FRAM, the ferroelectric capacitor and the MOS transistor are connected through a conductive plug. A diffusion barrier layer, for example, a titanium nitride (TiN) layer, is formed between the conductive plug and the lower electrode of the ferroelectric capacitor in order to prevent impurities from being diffused from the conductive plug upwards.
The diffusion barrier layer is oxidized during the annealing process for crystallization of the ferroelectric layer. Thus, a gap may be formed between the conductive plug and the lower electrode.
Also, since the conventional FRAM is formed using CMOS processes, it is difficult to form a transparent FRAM, thus limiting the applications of the conventional FRAM. For example, a smart card in which the conventional FRAM is embedded can provide no functions other than data storage.
Further, since the conventional FRAM is formed using high temperature processes, elements that have already been formed may be damaged during the high temperature processes.